People exposed to low-gravity environments during space travel are prone to losing bone density and muscle mass resulting from decreased resistance during ordinary movements. Astronauts on a space station do not need to support their full weight as they would while walking on Earth. Resistance training on Earth is an approach to minimizing the de-conditioning effects of space travel. While resistance training on Earth is beneficial and healthful to humans, such training in space is also important in low-gravity (less than Earth's gravity) environments for maintaining health and fitness. Many inventors have addressed the need for resistance training, and some devices are particularly intended for use in microgravity environments.
The International Space Station provides physical exercise equipment for its astronauts/cosmonauts to counter the de-conditioning effects of prolonged exposure to microgravity. One device, known as the Treadmill with Vibration Isolation and Stabilization (TVIS), provides walking, running, and deep knee-bending exercises. Another device known as the Resistive Exercise Device (RED) is designed to simulate weight lifting on Earth. A resistance force is coupled between the user and the equipment.
Ideally, exercise equipment for use in space should closely approximate the effects of gravity on Earth. Earth's gravity provides an essentially constant amount of weight (force) to a given mass. Consequently, a runner's legs would weigh the same throughout the running motion. Free weights, which are among the best source of resistance training on Earth, can provide a constant level of resistance throughout a range of movements as a result of gravity, i.e., a weight lifted one inch off a surface on Earth exerts the same constant force when the weight is lifted 20 inches off the surface. By contrast, machines which generate forces through spring-type resistance elements typically do not provide the constant force through displacement characteristic of free weights, and are often poor at duplicating the effects of gravity.
Without simulating the effects of gravity, exercise equipment in space may lead to possible distortion of body movements by exposing users to resistive forces unlike those experienced on Earth. For example, simulated treadmill running in space using a non-uniform resistance would train the body differently than would running while on Earth. Space travelers might therefore have problems readjusting to their normal routines on Earth. The exercise equipment ideally would provide the same force in space which the user would experience by a constant weight force on Earth, regardless of how the user moves, and thus behave like free weights on Earth, over a range of motion.
Although free weights are beneficial on Earth, they do not “weigh” anything in zero gravity environments. Free weights are not even practical for space travel to low gravity environments, such as the moon, because their size and weight would be too taxing on the payload. U.S. Pat. No. 4,944,511 discloses exercise equipment intended to address the inherent drawbacks of free weights by using resistance elements. However, this device suffers from the shortcomings discussed above related to the use of the equipment.
U.S. Pat. No. 6,126,580 discloses an exercise device for use in micro-gravity environments. The device uses resistive elements whose level of resistance increases with displacement. To counteract this increasing resistance, the device incorporates a pulley having a progressively increasing diameter, thus increasing the leverage acting against the resistance element.
U.S. Pat. No. 6,120,423 also addresses the need for exercise equipment in space to compensate for the constant force displacement characteristic of free weights on Earth. “Constant force” springs are used. This equipment also suffers from the shortcomings of other exercise machines. The size and weight of payloads in space travel are crucial, because they directly influence factors such as fuel consumption and spatial limitations. Payload items in space travel, such as exercise devices, must be designed to minimize both size and weight.
Another limitation of prior art exercise devices is the mechanism for selecting and adjusting the level of resistance for a particular user. With free weights used on Earth, selecting a level of resistance may include the simple task of interchanging a number of weights between a piece of equipment and a storage rack. Exercise equipment in space ideally may be used by various individuals with different strengths, and each individual also preferably may easily alter the force (energy) required to move over a particular range of motion.
Machines using alternatives to free weights incorporate a number of methods for selecting and varying resistance. U.S. Pat. No. 6,117,409 discloses the use of a screw mechanism for adding or subtracting plates from a stack. U.S. Pat. No. 6,120,423 proposes a plurality of sockets for receiving adjustable, detachable resistance mechanisms. U.S. Pat. No. 4,944,511 describes the use of a resistance element having an adjustable level of tension. Other patents of interest include U.S. Pat. Nos. 5,509,870, 5,685,811, 5,839,997, 5,898,111, 5,971,899, and 6,117,049. These prior art techniques do not adequately satisfy the rigorous requirements for exercise equipment to be used in low gravity environments.
The present apparatus surpasses the prior art, offering an improved exercise device for use in various environments, and particularly a low gravity environment. The exercise device closely duplicates the effects of gravity, and is easily adjusted. The exercise equipment is easily adjusted for a predetermined amount of restrictive forces, and is also highly efficient in terms of spatial and weight limitations for space travel.